adding code examples

README.md

@@ -59,6 +59,67 @@ _Note: in the examples below, make sure to set the latest version when you use i
   </script>
   ```
 
+In all cases, you can use this sample code to decode an image:
+
+```js
+const file = fs.readFileSync('./temp/0002.heic');
+
+const decoder = new libheif.HeifDecoder();
+const data = decoder.decode(file);
+// data in an array holding all images inside the heic file
+
+const image = data[0];
+const width = image.get_width();
+const height = image.get_height();
+```
+
+In NodeJS, you might use this decoded data with other libraries, such as `pngjs`:
+
+```js
+const { PNG } = require('pngjs');
+
+const arrayBuffer = await new Promise((resolve, reject) => {
+  image.display({ data: new Uint8ClampedArray(width*height*4), width, height }, (displayData) => {
+    if (!displayData) {
+      return reject(new Error('HEIF processing error'));
+    }
+
+    resolve(displayData.data.buffer);
+  });
+});
+
+const imageData = { width, height, data: arrayBuffer };
+
+const png = new PNG({ width: imageData.width, height: imageData.height });
+png.data = Buffer.from(imageData.data);
+
+const pngBuffer = PNG.sync.write(png);
+```
+
+In the browser, you might use this decoded data with `canvas` to display or convert the image:
+
+```js
+const canvas = document.createElement('canvas');
+
+canvas.width = width;
+canvas.height = height;
+
+const context = canvas.getContext('2d');
+const imageData = context.createImageData(width, height);
+
+await new Promise((resolve, reject) => {
+  image.display(imageData, (displayData) => {
+    if (!displayData) {
+      return reject(new Error('HEIF processing error'));
+    }
+
+    resolve();
+  });
+});
+
+context.putImageData(imageData, 0, 0);
+```
+
 ## Related
 
 This module contains the low-level `libheif` implementation. For more user-friendly functionality, check out these projects: